US2502100A - Pot type fuel burner having improved combustion characteristics - Google Patents

Description

Mara] 28, 1950 LITTLE POT TYPE FUEL BURNER HAVING IMPROVED COMBUSTION CHARACTERISTICS Flled March 18, 1946 /NVENTO HAEEY. CI L/7'7ZE forming partv of the specification,

Patented Mar. 28 1956 UNITED STATES PATENT OFFICE.

POT TYPE FUEL BURNER; HAVING PROVED COMBUSTION CHARACTER IS-TIC'S This invention relates to apparatus for vaporizing and burning hydrocarbon fuel.

An object of the invention is to provide improved combustion in a natural draft type liquid fuel burner wherein means is provided in the fuel mixture discharge orifice which functions to cause turbulenceand admixture of air in the fuel stream issuing from said orifice so as to effect immediate and complete combustion throughout the crosssectional area. of said stream without producing objectionable vibration and to spread the flame, when the burner is operating on low fire, diametrically in contrast to the inward diametrical concentration of the; flame on low draft which usually occurs in burners of this general type.

. A. still further object of the invention is to provide a deflector ring structure adapted for ready incorporation in conventional type natural draft liquid fuel burners by means of which the combustion performance of these burners may be diately above the burner orifice so as to force j dense core portions of the vapor stream. rising from. the orifice outwardly to enrich. the leaner circumferential zone of the stream.

The invention possesses other objects and features. of. advantage, some of which, with. the. foregoing, will be: set forth, in the following descrip tion of the. preferred form. of the. invention which is; illustrated in the drawings accompanying and It is to be understood, however... that variations in the showmade by the said drawings and description vmay be adopted within the scope of the invention asset forth in the claims.

Referring to the drawings:

' .Figure l. is a vertical sectional view of the buzzer-structure of the present invention as applied to a natural draft type burner.

. Figure 2 lsy'a top plan view of the burner shown in Figure 1,, but withv the superstructure omitted.

Figure-.3 an enlarged vertical sectional. view of one'of thedefiector wings. The plane in which the.- view is taken is indicated. by the line 33 oil Figure 1.. I

In liquid fuel: burners of the surface-evaporation natural-draft type, a flow of fuel is maintained. into and. over the bottom of a chamber within which. vaporization of; the fuel takes place and fromv which streams of the vapor rise. up-

wardly through ayburner throat or orifice provided in the top of the chamber. Vaporization of the fuel within the chamber may be accomplished by auxiliary heating means but the conventional practice is to expose the film or pool of fuel on the chamber bottom to heat radiated by combustion above the burner throat or orifice, which combustion is. sustained by the introduction into the chamber of a fiow of proper proportions of air to form, with the fuel vapor, a readily ignitable fuel mixture. A burner which operates onv this general principle is, shown in Figure 1 and comprises a housing 6, formed with an. internal chamber 1, having a top wall 8, provided with an orifice 9, and side walls I! having primary air inlets l2 therein. Fuel oil introduced into the chamber 1 through a suitable supply conduit, not shown, is allowed to fiow over the bottom [3 where vaporization thereof maybe started by an electrically heated coil 14 and continued by heat radiated downwardly through. the orifice 9 by the ignited fuel mixture. In the aforesaid types of burners, the stream of fuel mixture rising through the orifice 9 will be found to have an axial core comprising a comparatively dense concentration of fuel vapor while the peripheral portions of the stream contain a preponderance of air. This is due to the fact that fuel vapor rises directly from the bottom I 3 of the chamber and upwardly through the orifice 9 while the primary air enters the stream from the sides thereof. Ihus there is little chance for the air and fuel vapor to thoroughly mix before they pass upwardly out of the orifice 9 and the resulting flame will be long, converging and con.- centrated in the center area of the combustion chamber or other space or structure superposed above the burner. The products of combustion under such conditions will be extremely sooty, will produce little useful heat and will deposit carbon in the burner and stack. Improved admixture of the air and vapor has been achieved in. some instances by introducing. to the stream, immediately upon emergence thereof from the chamber orifice, natural drafts of secondary air so as to more or less penetrate. the stream and thereby provide a more readily combustible mixture. In other instances, secondary air has been introduced to the vapor stream by annular deflectors arranged concentrically with the flow and adapted to project the air radially into the latter so as to effect deeper penetration thereofand consequently a. better admixture of the two fluids. The improvementof this condition, however, sets up a resultant undesirable condition in that the complete circumferential impingement of the. sec

ondary air flow either rectangularly to the vapor flow or angularly inclined in the direction of movement thereof, effects a certain amount of radial compression in the stream which adds to the resultant height of the flame and produces an improper concentration of heat against and in the center of the superposed surface toward which the flame is directed.

In accordance with the present invention, I have provided a structure which overcomes to a large degree the several objectionable features outlined above. As may be best seen in Figure l, I provide between a superposed combustion chamber I and the vaporization orifice 9, a base ring member having a preferably circular disk flange I 7, which may be attached by bolts or otherwise to the top wall 8 of the burner, and which is provided with a central passage l8 coaxial with the'orifice 9. Bordering the passage IB is an upwardly extending collar l9 provided with peripherally spaced, radially extending ribs 2| which serve to increase the exposed surface of the secondary air stream. In one form of my invention I provide the flange I! with outer, circumferentially spaced pads 22 which are engaged by a marginal recess 23 formed peripherally of a flange 24, the latter being car-'- ried by a cylindrically tubular orifice ring 26 whose internal passage 27 is coaxial with and forms an extension of the passage H3. The flange 24 it will be noted is spaced vertically from the flange I! so as to form therebetween a secondary air passage 28 which also includes the spaces between adjacent pads 22 and those between adjacent ribs 2|.

The orifice ring 26 terminates a short distance above the collar IS in an end surface 29 from which extends, radially inwardly of the ring, a plurality of deflector wings 3|. The Wings are preferably arranged in opposed pairs and as will be seen in Figure 2, two pairs or four wings are provided and the wings spaced apart 90. Each of the deflector wings, as shown in Figure 3, is substantially semi-cylindrical in cross-sectional form with its concave surface or channel 32 facing the passage 21 and each wing slopes upwardly and inwardly from the ring 26 at a rather critical angle which, as operational tests have proven, should best be approximately twenty-four degrees from a horizontal plane rectangularly intersecting the vertical axis of the burner. In Figure 1 of the drawing it will be seen that planes extended from the ends of the wings and coinciding with the lower angular surfaces thereof will intersect at a common apex which is centered just slightly above the extreme top of the burner. The confronting ends of opposed wings are spaced from each other to form a central unobstructed opening 33 extending from the bottom l3 entirely vertically through the burner, while at the same time the wings 3| form a desirable obstruction to fluid flow from the burner passage 21 by creating turbulence in the vapor stream, the degree of such obstruction having been determined by tests to give the best burner performance when such obstruction is approximately thirty percent of the total area of the burner orifice. The arrangement of the wings 3| also provides a cruciform burner orifice which serves a useful purpose as will be presently explained.

When fuel is vaporized by the heating coil I4, the vapor rises upwardly in the chamber 1 toward and through the orifice 9, primary air simultaneously being drawn into the chamber through the apertures |2 to flow upwardly with the vapor and to intermix therewith. The vapor however is warmer than the primary air and the resulting stream flowing through the orifice will have a central core of comparatively dense vapor and a peripheral zone consisting substantially of air. Under these conditions, the proper intermixture of the vapor and air to produce combustion will not occur until the stream has passed upwardly out of the orifice for a considerable distance. This. causes the production of a tall diametrically narrow flame which due to retarded combustion will cause a deposit of considerable hard carbon and soot on surfaces which may be contacted by the flame, such as the bottom of the boiler l6, superposed above the burner. In the burner of my invention, however, the secondary air flowing through the passage 28 between the flanges I! and 24 rises upwardly along the inner surface of the ring 26 and in concentric relationship with the vapor and air stream issuing from the orifice l8. As portions of the secondary air current contact the channels of the wings 3|, the former will be caused to flow radially inwardly and to be projected from the ends of the wings in separate, narrow jets which criss-cross the vapor stream immediately above the upper ends of the wings. This, as tests have shown, will force the jets of secondary air completely through and beyond the vapor stream and cause immediate and thorough mixing of the air and fuel vapor in the proper proportions to produce complete and highly eflicient combustion. A principal effect, however, is the lateral spreading of the flame by the crossed secondary air jets r which is productive of a short, hot and evenly distributed fire which greatly enhances the efficiency of the burner. The diverted secondary air flow caused by the wings also effects the establishment of a pressure area over the center of the vapor stream which forces a certain portion of the vapor stream rising through the orifice l3 to flow radially outwardly into the spaces 35 between the wings so as to enrich the normally lean preponderant air flow which rises therethrough. The concave form of the wings will trap the portions of secondary air flowing therealong and will prevent lateral spreading thereof beyond the sides of the wings until the air is discharged into and through the core of the vapor stream.

When the burner has been in operation but a short time, the comparatively thick metal parts of the base and orifice rings will become quite hot and this heat will travel by conduction to the extremities of the rings. Thus the secondary air, from the moment it enters the passage 28 will be flowing between or in contact with hot surfaces and, by the time thatit engages the vapor stream, will have absorbed suflicient heat to accelerate its flow and to assist combustion by breaking up any oversize droplets of fuel which may be present in the stream. In this respect, the ribs 2| serve the purposes of heat conductors from the collar I9 and force the secondary air to flow through a plurality of individual passages in which it will absorb materially mor heat than it would otherwise acquire in passing between a plain collar and the adjacent surface of the ring 26. The substantial cast construction of the base and orifice'rings serves to effectively conduct and retain the heat absorbed thereby from the burner flame, and the substantially semi-cylindrical cross-sectional form of the wings produces an additional ad vantageous resultin that th heat reflected from the underside thereof will be focused into the chamber 7, below the opening l8 thereof and at the center of the vapor stream and serve to additionally heat the flow of vapor and primary air rising from the chamber toward the opening. As a result of these features a flame is produced which is short and at the same time has a relatively great spread.

The angular positioning of the Wings 3! is rather critical and, as repeated tests have shown best results have been attained with the wings inclined at approximately twenty-four degrees with respect to the horizontal. This angle not only seems to offer the least resistance to natural fiow of the fuel vapor and air but also substantially eliminates vibration, that is, the tendency of the flame to oscillate upwardly and downwardly through the burner orifice due to varying proportions of air and vapor mixture. A further effect of th Wings is to spread the flame into the spaces 35 between the sides of the wings during operation at low fire. This is believed to be due to the fact that although the vapor flow is throttled, the flow of secondary air is not and I the latter in flowing outwardly under the upper lips of the wings will create a reactance pressure downwardly into the burner orifice sufiicient to effect the said spreading of the flame. Such flame distribution will produce a far better and more uniform heating of the superposed object such as the boiler 16 than would a centrally concentrated flame which might otherwise be produced.

I claim:

1'. In a natural draft oil burner comprising a housing provided with inlets for primary air and a burner orifice in the top of the housin through which a. stream of fuel vapor and primary air may issue to create a flame above said orifice, a member secured to the top of the housing provided with a passageway coaxial with the orifice, an orifice ring spaced vertically above said member to provide therebetween secondary air passages through which secondary air may flow, said orifice ring extending upwardly in a substantially smooth wall and terminating in an opening substantially coextensive with and forming an extension of said passageway and orifice, and wing members having at least the curvature of said ring carried by said orifice ring, extending radially inwardly and upwardly from the upper end thereof and relatively widely spaced throughout their length, having confronting ends widely spaced from each other to provide an unobstructed passageway for the flame and to intercept portions of said secondary air flow for projecting said portions diametrically through said stream.

2. In a natural draft oil burner comprising a housing provided with inlets for primary air and a burner orifice in the top of the housing through which a stream of fuel vapor and primary air may issue to create a flame above said orifice, a member secured to the top of the housing provided with a passageway coaxial with the orifice, an orifice ring spaced vertically above said member to provide therebetween secondary air passages through which secondary air may fiow,

said orifice ring extending upwardly in a substantially smooth wall and terminating in an opening substantially coextensive with and forming an extension of said passageway and orifice, and wing members carried by said orifice ring, extendin radially inwardly and upwardly from the upper end thereof and relatively widely spaced throughout their length, havin confronting ends widely spaced from each other to provide an unobstructed passageway for the flame, said wing members having concavities confronting said secondary air flow to intercept in said concavitie-s portions of said secondary air flow and direct said portions in separate, comparatively narrow jets diametrically through said stream to a focus at a point above said wing members.

3. In a natural draft oil burner comprising a housing provided with inlets for primary air and a burner orifice in the top of the housing through which a stream of fuel vapor and primary air may issue to create a flame above said orifice, a member secured to the top of the housing provided with a passageway coaxial with the orifice, said member having an upwardly extending collar with peripherically spaced radially extending ribs bordering the passage, an orifice ring spaced vertically above said member to provide therebetween secondary air passages through which portions of secondary air may flow axially of said stream, said orifice ring extending upwardly in a substantially smooth wall and terminating in an openin substantially coextensive with and forming an extension of said passageway and orifice, and wing members carried by said orifice ring, extending radially inwardly and upwardly from the upper end thereof and relatively widely spaced throughout their length, having confronting ends widely spaced from each other to provide an unobstructed passageway for the flame, said wing members having arcuately shaped channels of substantially uniform cross-section throughout confronting said secondary air fiow to intercept in said channels other portions of said secondary air flow and direct said other portions in separate, comparatively narrow jets diametrically through said stream to a focus at a point above said wing members, said wing membersbeing arranged to radiate heat to a focus located below said orifice.

HARRY C. LITTLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,633,549 Little June 21, 1927 1,897,314 Little Feb. 14, 1933 2,072,048 Leonard Feb, 23, 1937 2,074,087 Nuetteman et a1. Mar. 16, 1937 1,109,946 Little Mar. 1, 1938 2,287,361 Suchland June 23, 1942 2,311,570 Pyle Feb. 16, 1943 2,337,673 McCurtain Dec. 28, 1943 2,401,086 Little May 28, 1946

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